THE WELSH SLURRY TECHNOLOGY THAT'S GIVING SOME SURPRISING RESULTS!
New technology that extracts water from slurry could be a big money saver for cattle farms – while slashing the risks of watercourse pollution at the same time.
Initial trials at Gelli Aur, Coleg Sir Gâr’s research farm in Carmarthenshire, suggest savings of nearly £50,000-a-year were possible for the holding’s 500-cow dairy herd.
In its first week of operation the system had already exceeded expectations, separating 90% of liquids from the 35 tonnes of slurry being processed each day.
Swansea-based Power and Water (P&W), the company behind the technology, had expected to extract just 80% of the liquids.
The £1.1m Prosiectslyri Project is still in its infancy and researchers anticipate a further two years of refinements before the equipment is ready to be rolled out.
Gelli Aur farm manager John Owen, who is managing the project, said the final system must be appropriate for all farms, whatever their scale.
“It is not just about the big boys, it has to be suitable for everyone,” he said.
“If it wasn’t it wouldn’t make much of a difference to overall water quality.”
Last week more than 250 producers attended an open day at Gelli Aur, a Farming Connect demonstration unit, to see how the treatment plant works.
Two separation systems are being trialled. One uses centrifugal force to remove the solids and the other, a screw press filter, forces slurry through a mesh screen.
Slurry is pumped into the separators and, once water has been extracted, the residue is a tenth of its original volume.
This solid material drops into a storage area before being scooped up and stored in a covered area, ready for spreading.
The filtered liquid, which is around 4%-5% dry matter (DM), passes to another treatment area. In this, a patented oxidation system breaks down the ammonia into nitrogen and hydrogen.
It also removes any remaining solids, which are routed back and added to the compressed slurry beneath the separator.
P&W CEO Gareth Morgan said the centrifuge system is more energy intensive but produces more solids. The screw press would be much cheaper to install but there is less separation.
“We will need to establish which produces the optimum results,” he said.
Mr Morgan said the purification process needs further work as the filtered water is not yet clean enough for discharge into local watercourses or for re-use on farms.
But this is within reach. “We are refining the processes as we go along,” he said.
One potential stumbling block is the need to analyse treated water before it is discharged. The project – RDP-funded by the Welsh Government – is working with Natural Resources Wales to define what the quality parameters should be for discharged water.
Initial work suggests substantial savings are possible, especially for a large dairy unit such as Gelli Aur’s.
Compressed slurry from the college farm, with its higher nutrient contents, could mean annual savings of £16,908 on bagged fertiliser.
Re-using the water, and reducing the spreading and diesel costs, would result in further cost savings of £32,296.
Slurry is a nutrient for grass but a pollutant in rivers, so reducing its volume was a win-win for farmers, said Dewi Hughes, Farming Connect’s technical development manager.
As well as will minimising the pollution risks, slurry separation should reduce storage requirements, he said.
“There is a real appetite for this type of technology,” he added.